Here's a link to a wheel and tire size comparison chart, http://www.rimsntires.com/specspro.jsp it allows you to plug in your wheel and tire dimensions and the wheel and tire sizes your thinking about and get the clearance differences. I just put 18x9.5 rims with a 23mm offset on the rear with 275/35-18 and 18x8 with 30mm offset and 235/40-18 up front. Still not much traction but the 351 with the massive cam and and performance parts, t5, and 3.73 rear end gears who would expect traction with just 275 width tires (might need a NASCAR restrictor plate).
